Orientation sensor utilizing intra-pattern property measurements

ABSTRACT

An orientation sensor capable of generating at least one output signal indicative of a particular orientation parameter is described. The orientation sensor comprises a sensor housing defining a closed internal chamber including a first internal surface. The first internal surface supports a first electrically conductive pattern which itself forms part of a sensing arrangement. The first electrically conductive pattern includes an arrangement of electrically isolated segments in a predetermined configuration. A flowable material is contained within the internal chamber, which flowable material contacts a portion of the first internal surface dependent upon the value of the particular orientation parameter. An electrical property is measurable between the segments such that the orientation parameter can be determined using the output signal based only on the electrical property and, therefore, only on the portion of the first internal surface contacted by the flowable material. Thus, intra-pattern measurements yield the measured property without the need for conductive members distributed along the length of the chamber. A combination pitch/roll sensor is described in which a single electrically conductive pattern cooperates with the flowable material so as to produce independent electrical signals corresponding to the pitch and roll of the housing. In one aspect, first and second electrically conductive patterns are provided at opposing ends of a flowable material chamber. Use of signals from the patterns results in ratiometric cancellation of temperature error.

[0001] This is a continuation application of copending prior applicationSer. No. 09/995,379, filed on Nov. 26, 2001, which is a continuationapplication of prior application Ser. No. 09/461,936, filed on Dec. 15,1999, now issued as U.S. Pat. No. 6,351,892 on Mar. 5, 2002, thedisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the field oforientation sensors and, more particularly, to an orientation sensorincluding a conductive pattern including isolated conductive segmentsconfigured for segment to segment (hereinafter intra-pattern) propertymeasurements useful in establishing one or more orientation parameters.The sensor is suitable for use in applications such as, for example,monitoring a remotely controlled underground boring device.

[0003] A number of orientation sensors have been designed especially foruse in remote controlled underground boring devices. As will be seen,these prior art devices have shared a basic design concept.

[0004] One example of a prior art orientation sensor in the form of aroll sensor is disclosed in U.S. Pat. No. 5,174,033 (Rider). FIGS. 1 and2 are partial reproductions of FIGS. 4 and 5, respectively, of the Riderpatent. FIG. 1 shows a roll sensor generally indicated by the referencenumber 10. Sensor 10 includes a substrate 12 and a cup-shaped member 14which is sealed to substrate 12 by an O-ring 16 in a way which defines acavity 18. A conductive fluid 20 is contained by cavity 18.

[0005] Attention is now directed to FIG. 2 in conjunction with FIG. 1.FIG. 2 illustrates a plurality of capacitor electrode plates 22 whichare formed on the inner surface of substrate 12. Electrical connectionsto capacitor electrode plates 22 are accomplished via a plurality ofelectrically conductive leads 24. Cup-shaped member 14 serves as agrounded electrode common to all of electrode plates 22. Duringoperation, roll sensor 10 is designed to spin in the plane of FIG. 2,oriented such that gravity causes fluid 20 to continuously flow into thebottom portion of the cavity (FIG. 1). The roll orientation of sensor 10is determined by measuring the capacitance between individual electrodeplates 22 and cup-shaped member 14 as influenced by fluid 20. It isimportant to note that measurements are taken, in essence, between theends of the device. Moreover, it is submitted that prior art orientationsensors, in general, operate under the concept of using measurementstaken along the length of the device. That is, by using electricallyconductive members positioned at least at the ends of the device and/orcentered therebetween or at other intermediate locations. For otherexamples, see U.S. Pat. Nos. 4,674,579, 4,714,118 and 5,726,359. As willbe seen, the present invention eliminates the need for an implementationhaving electrodes at both ends of a device or spaced apart therebetween,introducing a highly advantageous and heretofore unseen configurationuseful in measuring pitch and/or roll.

SUMMARY OF THE INVENTION

[0006] As will be described in more detail hereinafter, there isdisclosed herein an orientation sensor capable of generating at leastone output signal indicative of a particular orientation parameter. Theorientation sensor comprises a sensor housing defining a closed internalchamber including a first internal surface. The first internal surfacesupports a first electrically conductive pattern which itself forms partof a sensing arrangement. The first electrically conductive patternincludes an arrangement of electrically isolated segments in apredetermined configuration. A flowable material is contained within theinternal chamber, which flowable material contacts a portion of thefirst internal surface dependent upon the value of the particularorientation parameter.

[0007] In one aspect of the invention, an electrical property ismeasurable between the segments such that the orientation parameter canbe determined using the output signal based only on the electricalproperty and, therefore, only on the portion of the first internalsurface contacted by the flowable material. Thus, intra-patternmeasurements yield the measured property without the need for conductivemembers distributed along the length of the chamber.

[0008] In another aspect of the invention, the particular orientationparameter is pitch. In this instance, a first electrically conductivepattern includes first and second electrically isolated segmentsdefining a gap therebetween on the first internal surface such that thevalue of the electrical property is in proportion to an area of the gapcovered by the flowable material between the first and second segmentswhich, in turn, is in proportion to the pitch so as to cause the valueof the electrical property between the first and second segments tochange in response to changes in pitch.

[0009] In still another aspect of the invention, the particularorientation parameter is roll angle. In this instance, the firstelectrically conductive pattern includes at least first and secondelectrically isolated segments defining a first roll sensing gaptherebetween on the first internal surface such that the value of theelectrical property is in proportion to an area of the roll sensing gapcovered by the flowable material between the first and second segmentswhich, in turn, is in proportion to the roll so as to cause the value ofthe electrical property between the first and second segments to changein response to changes in roll. In one feature, the electricallyconductive pattern defines a plurality of roll sensing gaps, each ofwhich covers a particular range of roll positions of the orientationsensor. In one preferred embodiment, the electrically conductive patterndefines three roll sensing gaps that are configured so as tosubstantially surround a common center point about which the orientationsensor experiences roll. Each roll sensing gap is used to produce anoutput such that the roll position of the orientation sensor isunambiguously identifiable either statically or dynamically.

[0010] In yet another aspect of the present invention, an orientationsensor is provided which is capable of generating at least two outputsignals indicative of a particular orientation parameter. Theorientation sensor comprises a sensor housing defining a closed internalchamber having first and second opposing internal surfaces. A firstelectrically conductive pattern is supported by the first internalsurface and a second electrically conductive pattern is supported by thesecond internal surface. The first electrically conductive patternincludes a first plurality of electrically isolated segments in a firstpredetermined configuration while the second electrically conductivepattern includes a second plurality of electrically isolated segments ina second predetermined configuration. A flowable material is containedwithin the internal chamber such that the flowable material contactsfirst and second portions, respectively, of the first and secondinternal surfaces. The respective areas of the first and second portionscontacted by the flowable material are dependent upon the value of theparticular orientation parameter in a way which influences an electricalproperty measurable between the segments disposed on the first andsecond surfaces such that the first electrically conductive patternproduces at least a first output signal and the second electricallyconductive pattern produces at least a second output signal. In onefeature of the present invention, each pattern produces its outputsignal substantially independent of the other pattern based on contactwith the flowable material.

[0011] In another feature of the present invention, the first and secondelectrically conductive patterns are identical and identically orientedsuch that combined use of the output signals to determine the value ofthe orientation parameter produces ratiometric cancellation oftemperature error.

[0012] In one implementation according to the present invention, acombination pitch and roll orientation sensor is provided having ahousing containing a flowable material which flows in the housing inresponse to the pitch and roll orientation of the housing. An electricalarrangement includes a single electrically conductive patterncooperating with the flowable material so as to produce independentelectrical signals corresponding to the pitch and roll of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention may be understood by reference to thefollowing detailed description taken in conjunction with the drawingsbriefly described below.

[0014]FIGS. 1 and 2 are prior art figures taken directly from U.S. Pat.No. 5,174,033 for use in conjunction with the discussion of the priorart appearing above.

[0015]FIG. 3 is a diagrammatic side view of an orientation sensormanufactured in accordance with the present invention, shown here toillustrate general aspects of its highly advantageous structure.

[0016]FIG. 4 is a diagrammatic illustration of one of two identicalprinted circuit boards used in the orientation sensor of FIG. 3, shownhere to illustrate the overall outline of the boards in conjunction witha highly advantageous electrically conductive sensing pattern that isdefined on the depicted side of each board.

[0017]FIG. 5 is a diagrammatic illustration showing an electricallyconductive pattern formed on the side of the printed circuit boardsopposing the side depicted in FIG. 4.

[0018]FIG. 6 is a diagrammatic/schematic illustration showing one highlyadvantageous manner of electrically interconnecting the printed circuitboards of the orientation sensor of FIG. 3 for purposes of measuringpitch orientation.

[0019]FIG. 7 is a diagrammatic/schematic illustration showing one highlyadvantageous manner of electrically interfacing with the printed circuitboards of the orientation sensor of FIG. 3 for purposes of measuringroll orientation, which simultaneously permits the use of the pitchmeasurement scheme shown in FIG. 6.

[0020]FIG. 8 is a plot illustrating normalized roll output signals fromthe orientation sensor and associated circuitry of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Having described FIGS. 1 and 2 previously, attention isimmediately directed to FIG. 3 which illustrates an orientation sensormanufactured in accordance with the present invention and generallyindicated by the reference numeral 100. It is noted that dimensions inFIG. 3 have been exaggerated for illustrative purposes. Sensor 100 ismade up of first and second printed circuit boards 102 a and 102 b,respectively. A cylindrical tube 106 includes openings which are sealedto the inner facing surfaces 108 a and 108 b of each of the printedcircuit boards so as to define a cavity 110. Tube 106 may be formed, forexample, from quartz or from other such suitable materials. In thispreferred embodiment, printed circuit boards 102 a and 102 b areidentical to one another, as well as being identically oriented ateither end of tube 106. It is to be understood, however, that aneffective orientation sensor may be produced using only one of theseprinted circuit boards by sealing off tube 106, for example, at thelocation of a dashed line 112, which is described in further detailbelow.

[0022] Attention is now directed to FIGS. 3 and 4. The latter figureillustrates a printed circuit board pattern 114 that is formed on innersides 108 a and 108 b of each of printed circuit boards 102 a and 102 b.The overall outline of the printed circuit boards is a “tombstone”configuration, however, it should be appreciated that any suitableoutline may be used so long as measurements can be obtained inaccordance with the teachings herein. Pattern 114 defines a highlyadvantageous configuration made up of individual, electrically isolatedsegments including one combination of segments for sensing pitch andanother combination of segments for sensing roll. Specifically, a firstsegment 120 and a second segment 122 comprise a pitch sensingarrangement defining a pitch sensing gap 124. The first segmentcomprises a circular shape with its center located at center point 128.Alternatively, segment 120 could comprise a ring shape or other suchsuitable form. Second segment 122 comprises a ring shape which islikewise centered on center point 128 such that its innermost edge isequidistant from the edge of segment 120 about its periphery. Duringoperation, orientation sensor 100 is designed to be mounted, forexample, in the drill head of a boring tool such that roll takes placeabout an axis 126 (FIG. 3) which passes through the center point 128(FIG. 4) of each of printed circuit boards 102 a and 102 b. Pitch, onthe other hand, is measured in terms of the angle φ, as indicated inFIG. 3, wherein an arrow 130 represents a horizontal orientation.

[0023] Still referring to FIGS. 3 and 4, the roll sensing combination ofsegments comprises segment 122 along with segments 132 a-c so as todefine first, second and third roll sensing gaps 134 a-c, respectively,which serve to surround center point 128. Each of segments 132 a-c isspaced uniformly apart from segment 122 by virtue of an appropriateradius centered upon center point 128. Therefore, each roll sensing gapcovers an arc of somewhat less than 120° and is arcuate in form having aconstant width. External connections are made via connection pads 136a-c wherein pads 136 a-c are connected to roll sensing segments 132 a-cwhile pad 137 is connected to segment 122. The connection pads areelectrically connected with their associated segments by appropriatelyconfigured traces. For purposes of clarity, the traces are identifiedusing the appropriate connection pad reference number. It is noted thatsegment 122 includes projections 138 a and 138 b. These projectionsserve to equalize roll signals obtained from the different roll sensingsegments by approximating that portion of trace 137 which extendsbetween roll sensing segments 132 b and 132 c.

[0024] Attention is now directed to FIGS. 3-5. FIG. 5 illustrates anelectrically conductive pattern 140 formed on outer sides 142 a and 142b of printed circuit boards 102 a and 102 b, respectively. Afeed-through 144 defining a through-hole is positioned encompassingcenter point 128 whereby to electrically connect a trace 146 andassociated connection pad with segment 120 of pattern 114 on theopposite side of the printed circuit board. Connection pad 146 isarranged so as to be positioned laterally between connection pads 136 aand 136 c of pattern 114 (comparing FIGS. 4 and 5) for purposes ofmaintaining signal isolation between segment 120 and the various othersegments. This purpose is also furthered by a ground segment 148 whichcovers essentially all of outer sides 142, but for trace/pad 146 and aspace 150 defined between ground segment 148 and trace/pad 146. It isnoted that patterns 114 and 140 may be modified in any suitable mannerin accordance with the present invention. For example, in pattern 114,roll sensing segments 132 a-c may be positioned (not shown) within theinterior of segment 122 while segment 120 may surround (not shown) theouter periphery of segment 122.

[0025] Still referring to FIGS. 3-5, chamber 106 is partially filledwith a flowable material such as, for example, a suitable conductivefluid 152 which is selected to function in the manner to be described.The fluid may readily be injected, for example, into chamber 106 throughfeed-through 144 of printed circuit board 102 a while air is allowed toescape from the feed-through of printed circuit board 102 b. Thereafter,the feed-throughs may be sealed using any suitable material such as, forexample, silicone sealant. One useful conductive fluid has been found tobe glycerin with a small quantity of saline solution added to providefor conductivity, as described in U.S. Pat. Nos. 5,155,442, 5,337,002,5,444,382 and 5,726,359 which are incorporated herein by reference. Inorder to function in the manner intended, and at the same time, optimizecontact with patterns 114 on surfaces 108 a and 108 b, chamber 106 isfilled with conductive fluid 152 to a predetermined level. As will beseen, the predetermined fluid level should be selected in view ofseveral considerations with regard to establishing an operational rangeof orientations to be detected. Thus, conductivity, as measured betweenany pair of segments defining a sensing gap, will vary based upon theportion of the sensing gap in direct contact with the conductive fluid.It is important to understand that flowable materials that enablemeasurement of electrical characteristics other than conductivity (suchas capacitance and inductance) may also be used in chamber 110. Forinstance, materials having dielectric characteristics are well suitedwherein capacitance measured between the segments of electricallyconductive pattern 114 varies in accordance with the portion of thefluid contacting the respective sensing gap. One example of a materialhaving such dielectric characteristics is liquid silicone.

[0026] Having generally described the structure of orientation sensor100, the pitch aspect of its operation will be described with referenceto FIGS. 3 and 6. For any particular pitch orientation within apredetermined operational range, some portion of each pitch sensing gap124 will be contacted by conductive fluid 152. FIG. 6 diagrammaticallyillustrates printed circuit boards 102 a and 102 b along with externalelectrical connections in a configuration for purposes of sensing pitch.The illustrated pitch measurement configuration utilizes a voltagesource 160 having a positive (+) terminal electrically connected toconnection pad 137 of printed circuit board 102 b and a negativeterminal (−) connected to pad 137 of printed circuit board 102 a. Forpurposes of illustrations only this is shown as a direct current source.In actual practice, the source would be alternating in order to avoidelectrolytic damage to the conductive fluid 152 and/or other parts ofthe orientation sensor 100. Connection pads 146 of printed circuitboards 102 a and 102 b are electrically connected with one another and apitch output 162 is taken from this connection. The variableresistivities between segments 120 and 122 of printed circuit boards 102a and 102 b caused by contact of conductive fluid 152 with pitch sensinggaps 124 of the respective printed circuit boards are illustrated byequivalent variable resistors ER164 and ER166. It is to be understoodthat these equivalent variable resistors each represent a lumpedresistance corresponding to the actual, distributed resistance producedby the corresponding pitch sensing gap in contact with conductive fluid152. Thus, in operation, the sensor illustrated in FIG. 6 functions asequivalent variable resistors ER164 and ER166 connected in series withone another across voltage source 160.

[0027] Continuing to refer to FIGS. 3-5, it should be appreciated thatthe illustrated pitch sensing arrangement is highly advantageous.Specifically, orientation sensor 100 is configured for roll about axis126. Segments 120 and 122 of each printed circuit board, therefore,define pitch sensing gap 124 in such a way that the gap surrounds centerpoint 128. Additionally, pitch sensing gap 124 is circular inconfiguration and centered on center point 128 so that contact of thepitch sensing gap with conductive fluid 152 is constant irrespective ofroll about axis 126 (assuming the proper characteristics of fluid 152,as described above). Therefore, printed circuit boards 102 a and 102 bprovide a constant pitch output signal for a fixed pitch orientation,which output signal is independent of roll. It should be appreciatedthat the pitch sensing gap may be configured depending on the specificintended application. For example, in a pitch sensor which is notsubjected to roll, in normal use the pitch sensing gap may be defined asa “stripe” having a vertical component of orientation. Any configurationof pitch sensing gap is suitable in this regard so long as the area ofthe gap contacted by conductive fluid 152 is proportional to pitchorientation.

[0028] Still considering the pitch orientation measurement configurationillustrated in FIG. 6, it is important to understand that each printedcircuit board produces a pitch signal independent of the other board.That is, each board measures pitch based solely on the resistivitypresent between segments 120 and 122 of pattern 114. In essence, themeasurements are taken in the plane of each printed circuit pattern.Therefore, as mentioned previously, only one of printed circuit boards102 a and 102 b is necessary for producing a pitch measurement.Applicants submit that such a configuration has not been seen in theprior art. Accordingly, an effective pitch sensor may be implemented byclosing chamber 110 at aforementioned line 112 such that the chamber isdefined between this line and printed circuit board 102 a. The conceptof independently produced measurements provides significant advantagesover the prior art for reasons to be described.

[0029] As discussed above, prior art orientation sensors requireelectrodes that are positioned at opposing ends of a chamber (see FIGS.1 and 2) and possibly centered or at other intermediate positionsbetween the ends of the chamber (not shown). Accordingly, such prior artarrangements measure the electrical property of interest as distributedalong the length of the chamber. The entirety of the chamber is thusinvolved in obtaining the desired measurement. In contrast, because theelectrically conductive pattern of the present invention independentlyproduces its measurement, the entirety of the flowable medium chamber isnot involved in generating the desired orientation signal. That is,measurements are localized at each printed circuit board. In and byitself, it is submitted that this feature provides a heretofore unseenopportunity for improvement in the accuracy of an orientation sensorusing a single flowable medium chamber. The significance of suchindependent readings will be described immediately hereinafter.

[0030] Referring again to FIGS. 3-5, it should be appreciated that theelectrical interconnection of printed circuit boards 102 a and 102 b inFIG. 6 utilizes the independently produced pitch signal of each board ina highly advantageous way. Specifically, as noted above, equivalentresistance 164 of circuit board 102 a and equivalent resistance 166 ofcircuit board 102 b are connected in series across voltage source 160with pitch output 162 being taken at the common connection between theequivalent resistances. It should also be appreciated that measurementstaken from each of the printed circuit boards are affected as a resultof changes in conductivity of electrically conductive fluid 152resulting from temperature changes. If only one printed circuit boardwere used, such temperature effects should be given consideration.However, in the circuit of FIG. 6, temperature equally affects the pitchsignal produced by each printed circuit board. Therefore, as a result ofthe series connection of equivalent resistances 164 and 166, thetemperature produced resistance changes are seen to essentially cancelone another. No provision other than the use of the illustratedinterconnection is required in order to realize this advantage.Therefore, in accordance with the present invention, this configurationis substantially immune to temperature induced error. It should beappreciated that the described temperature cancellation effects areratiometric in nature and are not limited to this specificconfiguration. That is, ratiometric cancellation will be exhibitedwhenever a ratio is taken between measurements produced by the printedcircuit boards 102 a and 102 b at either end of the orientation sensor.

[0031] Although the pitch measurements produced by printed circuitboards 102 a and 102 b are independent of each other, it should beappreciated that, for any particular pitch angle, the different portionsof each printed circuit pattern contacted by conductive fluid 152 are,in fact, interdependent. For this reason, pitch output 162 is unique forany particular pitch orientation within a specified operational range ofpitch angles. Specific details will be provided for establishing aparticular operational range at an appropriate point below. It should benoted that the sensitivity of the orientation sensor is proportional tothe length of tube 106 (FIG. 3).

[0032] Attention is now directed to FIG. 7 in conjunction with FIGS.3-5. FIG. 7 diagrammatically illustrates orientation sensor 100including external electrical connections made to printed circuit boards102 a and 102 b for use in sensing roll orientation. As mentionedpreviously, roll orientation sensing is accomplished using a particularcombination of segments including segments 132 a-c and segment 122, allof which cooperatively define roll sensing gaps 134 a-c. The externalcircuitry configuration of FIG. 7 may be used simultaneously with thepitch sensing configuration of FIG. 6 such that each of printed circuitboards 102 a and 102 b independently produces a pitch signal, but alsoindependently produces roll signals. To this end, voltage source 160 isapplied to connection pad 137 of each printed circuit board 102 a and102 b, as originally shown in FIG. 6 so as to apply voltage to segment122 of each printed circuit board 102 a and 102 b. Each one ofconnection pads 136 a-c for each printed circuit board 102 a and 102 bis connected to a circuit ground 170 through one of a plurality ofresistors indicated by the reference numbers R172 a-f, all of which havethe same value. Equivalent resistances of roll sensing gaps 134 a-c forprinted circuit board 102 a are indicated by the reference numbersER174, ER176 and ER178, respectively, while equivalent resistances ofroll sensing gaps 134 a-c for printed circuit board 102 b are indicatedby the reference numbers ER180, ER182 and ER184, respectively. Onceagain, it is to be understood that each of these equivalent variableresistors represents a lumped resistance corresponding to the actual,distributed resistance produced by the corresponding roll sensing gap incontact with conductive fluid 152. Therefore, a voltage divider isformed for each roll sensing gap comprising the resistance of the pitchsensing gap in series with one of resistors R172. Six roll outputs areindicated as ROLL_(a-f). For example, roll sensing gap 134 a of printedcircuit board 102 a, having an equivalent resistance represented byER174, is in series with resistor R172 a. The corresponding roll output,ROLL_(a), is taken from the connection of R172 a and connection pad 136a.

[0033] Attention is now directed to FIGS. 7 and 8. FIG. 8 illustratesoutput signals ROLL_(a-c) for counterclockwise roll in the directionindicated by an arrow 190. For purposes of clarity, output signalsROLL_(d-f) (independently produced by printed circuit board 102 b) havenot been illustrated. The specific position of printed circuit boards102 a and 102 b in FIG. 7 correspond to the roll position of 0° in FIG.8. Chamber 106 and the level of fluid 152 are also diagrammaticallyshown between the two printed circuit boards. In the position shown inFIG. 7, roll sensing gap 134 c is completely immersed in fluid 152. Rollsensing gap 134 a is partially immersed in the fluid and is beingfurther immersed by continuing rotation. Therefore, ROLL_(a) exhibits apositive slope at the 0° roll position. Roll sensing gap 134 b is alsopartially immersed in fluid, but is emerging from the fluid withrotation such that ROLL_(b) exhibits a negative slope at the 0° rollposition. It is apparent from FIG. 8 that the combination of these threeroll signals unambiguously identifies the roll position of orientationsensor 100 for any particular roll orientation under both static anddynamic conditions. Moreover, the roll output waveforms of FIG. 8contemplate the level of fluid 152 as being above center point 128 ofprinted circuit board 102 a since positive plateaus 192 of the rollsignal waveforms are longer in duration than negative plateaus 194. Thatis, the orientation sensor is pitched such that the roll sensing gapsare completely immersed in fluid 152 over an arc that is longer than thearc over which the roll sensing gaps are completely out of contact withthe fluid. This condition may be caused, for example, by a pitch, φ, ofapproximately −10% grade as indicated by fluid 152 which causes agreater proportion of fluid to contact printed circuit board 102 acompared with the portion contacting printed circuit board 102 b. Theusefulness of roll signals from the second printed circuit board will bedescribed immediately below.

[0034] Referring to FIGS. 3 and 4, the operational range of orientationsover which orientation sensor 100 is useful depends upon a number ofdifferent factors including the level of fluid 152, the length, L, ofchamber 110 (tube 106), the diameter of tube 106 and the widths of thevarious pitch and roll sensing gaps. In this regard, the overallcombination of these factors cooperate interactively to establish theoperational range of the sensor. An orientation sensor has been producedin accordance with this disclosure for use in a horizontal directionaldrilling application anticipating an operational pitch range ofapproximately ±100% grade. Specific dimensions of this workingembodiment include tube 106 having a length, L, of approximately 0.188inches and an inside diameter of approximately 0.375 inches. Pitchsensing gap 124 includes inner and outer diameters of approximately0.195 inches and 0.234 inches, respectively. Roll sensing gaps 134 a-cinclude inner and outer diameters of approximately 0.275 inches and0.313 inches, respectively. These dimensions may be modified in anysuitable way depending upon a specific application. For example, L maybe increased so as to increase the pitch sensitivity of the orientationsensor. Likewise, pitch sensitivity is increased by lowering therelative level of fluid 152. However, the effect of any modificationshould be considered with regard to other factors. For instance, if L isinordinately increased, the range over which fluid 152 contacts bothprinted circuit boards 102 a and 102 b will be decreased. The netresult, at high pitch, may be one printed circuit board completelycovered by fluid 152 while the opposing board makes no contact withfluid 152.

[0035] It should be appreciated that the roll output signals of printedcircuit board 102 b will essentially be identical to those obtained fromprinted circuit board 102 a when pitch angle φ is equal to zero. Ininstances where φ is not equal to zero, the output signals obtained fromone printed circuit board will vary from those of the other printedcircuit board dependent upon the specific value of φ. Because therotational motion of inner sides 108 a and 108 b of printed circuitboards 102 a and 102 b relative to axis 126 is opposite to one another,ROLL_(a) of printed circuit board 102 a corresponds to ROLL_(b) ofprinted circuit board 102 b while ROLL_(b) of printed circuit board 102a corresponds to ROLL_(a) of printed circuit board 102 b. While bothprinted circuit boards 102 a and 102 b independently produce rollsignals, the overall accuracy of orientation sensor 100 can be improvedeven further by utilizing the roll signals available from both printedcircuit boards. For example, all six of the roll signals may beconverted to digital signals using an analog to digital converter (notshown),provided to a microprocessor (not shown), and thereafter providedto a suitable arrangement, such as a display (not shown) for calculationand display of the roll position of the orientation sensor.

[0036] The roll sensing configuration disclosed in FIG. 7 herein may bemodified in an unlimited number of ways according to the presentinvention. For example, any number of two or more roll sensing gaps maybe utilized. In the instance where only roll is dynamically measured, aslittle as a single roll sensing gap is useful. For example, a rollsensing gap (not shown) may be configured including a varying, knownwidth which surrounds the center of rotation of roll of the orientationsensor. Dynamic analysis of the output from such a sensing gap can beused to uniquely identify any particular roll position. In this regard,any combination or configuration of the roll sensing gaps which uniquelyidentifies roll position of the orientation sensor is useful whetheroperable in static or dynamic conditions. Another possible modificationresides in providing printed circuit boards having sensing gaps ofdifferent configurations (not shown) at either end of chamber 106 or,alternatively, identical patterns offset with respect to one another maybe provided at either end of chamber 110. In this way, two roll sensinggaps may be used to uniquely identify the static roll position oforientation sensor 100.

[0037] Because the orientation sensor disclosed herein may be providedin a variety of different configurations and modified in an unlimitednumber of different ways, it should be understood that the presentinvention may be embodied in many other specific forms without departingfrom the spirit or scope of the invention. For example, electricallyconductive patterns may be provided in forms other than as electricallyconductive traces on a printed circuit board. In one such alternative,relatively rigid grid wires (not shown) may be used wherein the flowablemedium may flow around and between the grid wires. Therefore, thepresent examples and methods are to be considered as illustrative andnot restrictive, and the invention is not to be limited to the detailsgiven herein, but may be modified within the scope of the appendedclaims.

What is claimed is:
 1. A pitch sensor capable of generating at least oneoutput signal indicative of a pitch orientation of an axis about whichroll may occur, said pitch sensor comprising (a) a sensor housingdefining a closed internal chamber including a first internal surfacewhich is intersected at a point by said axis; (b) an arrangement ofelectrically isolated segments supported by said first internal surfaceso as to define a pitch sensing gap which at least substantiallysurrounds said point; and (c) a flowable material contained within saidinternal chamber, which flowable material contacts a portion of saidfirst internal surface, which portion is dependent upon the pitchorientation of said axis in a way which influences an electricalproperty measurable between the segments such that said pitchorientation can be determined using said output signal based only on theelectrical property.
 2. The pitch sensor of claim 1 wherein said gap isformed continuously and completely surrounding said point such that theelectrical property is unaffected by said roll and, therefore, theoutput signal for use in determining said pitch is provided irrespectiveof said roll.
 3. The pitch sensor of claim 1 wherein said flowablematerial is electrically conductive and wherein said electrical propertyis the electrical conductivity of the flowable material measured acrosssaid pitch sensing gap.
 4. The pitch sensor of claim 1 wherein saidflowable material is suitable for use as a dielectric and wherein saidmeasurable property is capacitance between the segments of said firstelectrically conductive pattern which varies across said pitch sensinggap based upon the presence of said flowable material in contact withsaid arrangement of electrically isolated segments.
 5. The pitch sensorof claim 1 wherein said arrangement of electrically isolated segmentsincludes first and second electrically isolated segments defining saidpitch sensing gap therebetween on said first internal surface such thatthe value of said electrical property is in proportion to an area ofsaid pitch sensing gap covered by said flowable material between saidfirst and second segments which, in turn, is in proportion to said pitchso as to cause the value of said property between the first and secondsegments to change responsive to the pitch.
 6. The pitch sensor of claim1 wherein said axis is substantially normal to said first internalsurface and wherein said pitch sensing gap is configured for providing acontinuous output signal for a fixed value of said pitch orientationirrespective of said roll.
 7. The pitch sensor of claim 6 wherein saidpitch sensing gap is circular in form having a center located at saidpoint.
 8. A method for producing a pitch sensor capable of generating atleast one output signal indicative of a pitch orientation of an axisabout which roll may occur, said method comprising the steps of: (a)arranging a sensor housing to define a closed internal chamber includinga first internal surface which is intersected at a point by said axis;(b) supporting an arrangement of electrically isolated segments on saidfirst internal surface so as to define a pitch sensing gap which atleast substantially surrounds said point; and (c) placing a flowablematerial in said internal chamber, which flowable material contacts aportion of said first internal surface, which portion is dependent uponthe pitch orientation of said axis in a way which influences anelectrical property measurable between the segments such that said pitchorientation can be determined using said output signal based only on theelectrical property.
 9. The method of claim 8 including the step offorming said pitch sensing gap to continuously and completely surroundsaid point such that the electrical property is unaffected by said rolland, therefore, the output signal for use in determining said pitch isprovided irrespective of said roll.
 10. The method of claim 8 whereinsaid flowable material is electrically conductive and wherein saidelectrical property is the electrical conductivity of the flowablematerial measured across said pitch sensing gap.
 11. The method of claim8 wherein said flowable material is suitable for use as a dielectric andwherein said measurable property is capacitance between the segments ofsaid first electrically conductive pattern which varies across saidpitch sensing gap based upon the presence of said flowable material incontact with said arrangement of electrically isolated segments.
 12. Themethod of claim 8 including the step of configuring said arrangement ofelectrically isolated segments to include first and second electricallyisolated segments defining said pitch sensing gap therebetween on saidfirst internal surface such that the value of said electrical propertyis in proportion to an area of said pitch sensing gap covered by saidflowable material between said first and second segments which, in turn,is in proportion to said pitch orientation so as to cause the value ofsaid property between the first and second segments to change responsiveto the pitch.
 13. The method of claim 8 wherein said axis issubstantially normal to said first internal surface and said supportingstep includes the step configuring said pitch sensing gap for providinga continuous output signal for a fixed value of said pitch orientation,irrespective of said roll.
 14. The method of claim 13 wherein said pitchsensing gap is configured as circular in form having a center located atsaid point.